<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <style>
        body{
             margin:0;
            padding:0;
            width:100%;
            height:100%;
            min-height:100%;
        }
        #container{
            position:relative;
            width:80%;
            margin:0 auto;
            min-height: 800px;
            border:1px solid red;
        }
        .Absolute-Center {
            background:#ccc;
            margin: auto;
            position: absolute;
            top: 0; left: 0; bottom: 0; right: 0;
            width:50%;
            height:50%;
            overflow: auto;
        }
    </style>
</head>
<body>
<div id="container">
    <div class="Absolute-Center">
        <div>fdsafdasfdsafdasfdsafdasfdsafdasfdsafdasfdsafdasfdsafdasfdsafdasfdsafdasfdsafdasfdsafdasfdsafdasfdsafdasfdsafdas</div>
    </div>
</div>
</body>
</html>